The present invention relates to a semiconductor device manufactured using a substrate including an epitaxial layer, a semiconductor substrate, a method for manufacturing a semiconductor device, and a method for manufacturing a semiconductor substrate.
Nitride semiconductors such as GaN and AlGaN are used as the substrates of high-voltage semiconductor devices and light-emitting devices. Nitride semiconductor substrates obtained by epitaxially growing a nitride semiconductor layer over a substrate including Si, sapphire, or the like are used for cost reduction purposes. However, the lattice constant of a nitride semiconductor differs from that of the material included in the substrate. Thus, many dislocations occur in the nitride semiconductor layer.
On the other hand, Japanese Unexamined Patent Publication No. 2004-146605 discloses the following technology. First, a first nitride semiconductor layer is epitaxially grown over a sapphire substrate. Next, ions are implanted into the first nitride semiconductor layer. At this time, ions are implanted to the extent that the first nitride semiconductor layer is not amorphized. Specifically, an implantation acceleration voltage of 20 keV and a dose amount of 1×1013 cm−2 are shown as ion implantation conditions. This Publication states that the ions implanted as described above can terminate dangling bonds made by the dislocations. Subsequently, a second nitride semiconductor layer is epitaxially grown over the first nitride semiconductor layer.